<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>背景图片</title>
  <style>
      .box {
          width: 600px;
          height: 300px;
          border: 2px solid red;
          background-image: url("./img/balloons.jpg");
          /*background-size: 150px 10em;*/
          /*background-size: contain;*/
          background-size: cover;
          background-repeat: no-repeat;
      }
  </style>
</head>
<body>
<div class="box">
</div>
</body>
</html>